package leetcode.editor.cn;

//给定两个整数数组 preorder 和 inorder ，其中 preorder 是二叉树的先序遍历， inorder 是同一棵树的中序遍历，请构造二叉树并
//返回其根节点。 
//
// 
//
// 示例 1: 
//
// 
//输入: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
//输出: [3,9,20,null,null,15,7]
// 
//
// 示例 2: 
//
// 
//输入: preorder = [-1], inorder = [-1]
//输出: [-1]
// 
//
// 
//
// 提示: 
//
// 
// 1 <= preorder.length <= 3000 
// inorder.length == preorder.length 
// -3000 <= preorder[i], inorder[i] <= 3000 
// preorder 和 inorder 均 无重复 元素 
// inorder 均出现在 preorder 
// preorder 保证 为二叉树的前序遍历序列 
// inorder 保证 为二叉树的中序遍历序列 
// 
// Related Topics 树 数组 哈希表 分治 二叉树 👍 1580 👎 0

//Java：【105】 - 从前序与中序遍历序列构造二叉树
public class ConstructBinaryTreeFromPreorderAndInorderTraversal_105{
    public static void main(String[] args) {
        Solution solution = new ConstructBinaryTreeFromPreorderAndInorderTraversal_105().new Solution();
                // TO TEST
    }
    
    //leetcode submit region begin(Prohibit modification and deletion)
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        TreeNode head = new TreeNode(preorder[0]);
        if(preorder.length==1) return head;
        int index =0;
        while (inorder[index]!=preorder[0]){
            index++;
        }
        int leftLength = index;
        head.left = buildSubTree(preorder, inorder, 1, leftLength, 0, index-1);
        head.right = buildSubTree(preorder,inorder,leftLength+1, preorder.length-1,index+1, inorder.length-1);

        return head;
    }

    public TreeNode buildSubTree(int[] preorder, int[] inorder,int left1, int right1, int left2, int right2){

        if(left1>right1) return null;
        TreeNode node = new TreeNode(preorder[left1]);
        int index =left2;
        while (inorder[index]!=preorder[left1]){
            index++;
        }
        int leftLength = index-left2;
        node.left = buildSubTree(preorder, inorder, left1+1, left1+leftLength, left2, index-1);
        node.right = buildSubTree(preorder,inorder,left1+leftLength+1,right1,index+1,right2);
        return node;
    }
}
//leetcode submit region end(Prohibit modification and deletion)
public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode() {}
    TreeNode(int val) { this.val = val; }
    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}
}
